Rambus Inc.

Patent Trials and Appeals Board

Feb 28, 2020

15165134 - (D) (P.T.A.B. Feb. 28, 2020)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
15/165,134 05/26/2016 Brian S. Leibowitz RA290.CIP1CIP1C1.B77 8106
38489 7590 02/28/2020
SILICON EDGE LAW GROUP, LLP
7901 Stoneridge Drive
Suite 528
PLEASANTON, CA 94588
EXAMINER
YU, LIHONG
ART UNIT PAPER NUMBER
2631
NOTIFICATION DATE DELIVERY MODE
02/28/2020 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
USPTO@dockettrak.com
art@siliconedgelaw.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte BRIAN S. LEIBOWITZ and BRUNO W. GARLEPP

Appeal 2019-001770
Application 15/165,134
Technology Center 2600
Before ST. JOHN COURTENAY III, LARRY J. HUME, and
PHILLIP A. BENNETT, Administrative Patent Judges.
BENNETT, Administrative Patent Judge.
DECISION ON APPEAL
STATEMENT OF THE CASE
Pursuant to 35 U.S.C. § 134(a), Appellant1 appeals from the
Examiner’s decision to reject claims 2, 3, 5–10, 19 and 20. Claims 1
and 11–18 are cancelled. Claims 4 and 21 are allowed. Claims 22–24 are
objected to. We have jurisdiction under 35 U.S.C. § 6(b).
We reverse.

1 We use the word “Appellant” to refer to the applicant as defined in
37 C.F.R. § 1.42(a). Appellant identifies the real party in interest as
Rambus, Inc. Appeal Br. 1.
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Application 15/165,134

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CLAIMED SUBJECT MATTER
The claims are directed to “DFE margin test methods and circuits that
decouple sample and feedback timing.” Spec., Title. Claim 2, reproduced
below with the disputed limitation in italics, is illustrative of the claimed
subject matter:
2. A receiver comprising:
a data input terminal to receive a stream of input data
symbols;
a first data sampler with first decision-feedback
equalization to sample the input data symbols and output a first
series of samples, the first decision-feedback equalization based
on feedback of the first series of samples;
a second data sampler with second equalization to sample
the input data symbols and output a second series of samples, the
second equalization based on an assumption for each preceding
data symbol absent consideration of any of the preceding data
symbols; and
a comparison circuit to compare the first series of samples
with the assumptions of preceding data symbols.
Appeal Br. 8 (Claims Appendix).
REFERENCES
The prior art relied upon by the Examiner as evidence is:
Name Reference Date
Henry US 4,285,046 Aug. 18, 1981
Arnon et al. US 4,864,590 Sept. 5, 1989
Lewyn US 6,100,834 Aug. 8, 2000
Ueno US 6,691,260 B1 Feb. 10, 2004
Chennakeshu et al. US 7,099,410 B1 Aug. 29, 2006
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REJECTIONS UNDER 35 U.S.C. § 103
Claims 2, 3, 5, 6, 19, and 20 stand rejected under 35 U.S.C. § 103(a)
as being unpatentable over the combination of Ueno, Henry and
Chennakeshu. Final Act. 2.
Claims 7, 9, and 10 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over the combination of Ueno, Henry, Chennakeshu, and
Arnon. Final Act. 6.
Claim 8 stands rejected under 35 U.S.C. § 103(a) as being
unpatentable over the combination of Ueno, Henry, Chennakeshu, Arnon,
and Lewyn. Final Act. 8.
ISSUE
Has the Examiner erred in finding Ueno, Henry and Chennakeshu
teach or suggest “the second equalization based on an assumption for each
preceding data symbol absent consideration of any of the preceding data
symbols,” as recited in claim 2?
ANALYSIS
Claim 2 recites “the second equalization based on an assumption for
each preceding data symbol absent consideration of any of the preceding
data symbols.” Appeal Br. 8 (Claims Appendix). In rejecting claim 2 as
obvious, the Examiner relies on both Ueno and Chennakeshu for teaching
this limitation. Specifically, the Examiner finds Ueno teaches “the second
equalization based on an assumption,” but that the assumption in Ueno is an
assumption for polarity, and not “for each preceding data symbol absent
consideration of any of the preceding data symbols” as recited in the claim.
Final Act. 3–4. To address this deficiency, the Examiner turns to
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Chennakeshu, finding that “Chennakeshu teaches an equalization based on
an assumption for each preceding data symbol absent consideration of any of
the preceding data symbols (see col. 1, lines 46–67, where Chennakeshu
describes a MLSE equalizer that uses two possible values for two previous
symbols, no consideration of actual values of previous symbols).” Final
Act. 5 (italics omitted). The Examiner concludes:
It would have been obvious to one of ordinary skill in the art at
the time the invention was made to modify the invention of Ueno,
and to include that the second equalization based on an
assumption for each preceding data symbol absent consideration
of any of the preceding data symbols, as taught by Chennakeshu,
thus allowing for coherent demodulation of multipath signals, as
discussed by Chennakeshu (see col. 1, lines 36-45).
Final Act. 5.
Appellant argues “[b]oth of Ueno's detectors are provided with
feedback from preceding symbols so neither employs equalization that is
‘absent consideration of any of the preceding data symbols’ as recited in
claim 2.” Reply Br. 4. Appellant contends that if Chennakeshu’s equalizer
was substituted for the equalizers in Ueno as proposed by the Examiner, then
neither of the equalizers in the resultant device would be provided
feedback—which is contrary to the claimed device which requires one
equalization performed using feedback, and one equalization without
feedback. Appeal Br. 5–6.
Appellant also challenges the Examiner’s rationale for combining
Ueno’s teachings with Chennakeshu’s, arguing that nothing in either Ueno
or Chennakeshu suggests “modifying Ueno's a dual-equalizer system to
support two different forms of equalization, one ‘based on feedback of [a]
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first series of samples’ and the other ‘absent consideration of any of the
preceding data symbols . . .’.” Reply Br. 4–5.
We are persuaded the Examiner erred in rejecting claim 2. We agree
with Appellant that Ueno fails to teach or suggest any equalization that is
“absent consideration of any of the preceding data symbols.” As correctly
explained by Appellant, Ueno’s Figure 13 shows that both detectors 92
and 96 receive preceding data symbols which are fed back via feedback
filters 93 and 97 and additional circuits 91 and 95. Thus, Ueno’s both of
data samplers utilize feedback-based equalization.
The cited portions of Chennakeshu teach the use of a “maximum-
likelihood-sequence-estimation (MLSE)” equalizer which does not perform
feedback-based equalization. Chennakeshu col. 1, ll. 36–67. The Examiner
finds that it would have been obvious to modify Ueno such that one of the
data samplers uses Chennakeshu’s equalizer and is not feedback-based, but
the other remains the same. Ans. 4. The Examiner finds that a person of
ordinary skill in the art would have been motivated to incorporate
Chennakeshu’s equalizer into Ueno’s device because it allows for coherent
demodulation of multipath signals. Although this reasoning may support
replacement of both of Ueno’s equalizers with Chennakeshu’s approach, the
Examiner does not sufficiently explain why a person or ordinary skill in the
art would have thought to replace one of Ueno’s equalizers with
Chennakeshu’s, while leaving the other the same.
The Examiner finds that “Ueno suggests that one equalization may
have a feedback, and the other equalization may not have a feedback.”
Ans. 4 (citing col. 2, ll. 50–54). However, we discern no such suggestion in
the cited portion of Ueno. We agree with Appellant that “Ueno appears to
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be referring to a control method that does not work for a multi-level DFE
with multiple paths despite applicability to a single feedback equalizer.”
Thus, Ueno does not suggest implementing a dual-equalizer system
supporting two different forms of equalization. The Examiner does not
identify any other record evidence that suggests the desirability of the
proposed modification. As such, we conclude the modification of Ueno
proposed by the Examiner uses the claimed invention as a roadmap, which
infects the proposed modification with impermissible hindsight bias, and we
do not sustain the rejection of claim 2.
For the same reasons, we also reverse the rejection of independent
claim 19, which recites the disputed limitation in commensurate form, as
well as of the rejections of remaining claims 3, 5–10, and 20, which depend
from independent claims 2 and 19.2
CONCLUSION
We reverse the Examiner’s decision to reject claims 2, 3, 5–10, 19 and
20 under 35 U.S.C. § 103(a).

2 Because we find these argument persuasive and dispositive of the
rejections made under § 103, we do not address Appellant’s remaining § 103
arguments.
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Application 15/165,134

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DECISION SUMMARY
Claims
Rejected
35 U.S.C.
§
Reference(s)/Basis Affirmed Reversed
2, 3, 5, 6,
19, 20
103 Ueno, Henry,
Chennakeshu
2, 3, 5, 6,
19, 20
7, 9, 10 103 Ueno, Henry,
Chennakeshu,
Arnon
7, 9, 10
8 103 Ueno, Henry,
Chennakeshu,
Arnon, Lewyn
8
Overall
Outcome
2, 3, 5–10,
19, 20

REVERSED